CEFR Language Exam Resource Centre
CEFR Language Exam Resource Centre

Modal Verbs – ISE II Trinity Grammar Function

Modal Verbs – ISE II Trinity Grammar Function

Click here to revise Modal Verbs

Modals (also called modal verbs, modal auxiliary verbs, modal auxiliaries) are special verbs which behave irregularly in English. They are different from normal verbs like “work, play, visit…” They give additional information about the function of the main verb that follows it. They have a great variety of communicative functions.

Here are some characteristics of modal verbs:

  • They never change their form. You can’t add “s”, “ed”, “ing”…
  • They are always followed by an infinitive without “to” (e.i. the bare infinitive.)
  • They are used to indicate modality allow speakers to express certainty, possibility, willingness, obligation, necessity, ability
Modal Verb Expressing Example
must Strong obligation You must stop when the traffic lights turn red.
logical conclusion / Certainty He must be very tired. He’s been working all day long.
must not prohibition You must not smoke in the hospital.
can ability I can swim.
permission Can I use your phone please?
possibility Smoking can cause cancer.
could ability in the past When I was younger I could run fast.
polite permission Excuse me, could I just say something?
possibility It could rain tomorrow!
may permission May I use your phone please?
possibility, probability It may rain tomorrow!
might polite permission Might I suggest an idea?
possibility, probability I might go on holiday to Australia next year.
need not lack of necessity/absence of obligation I need not buy tomatoes. There are plenty of tomatoes in the fridge.
should/ought to 50 % obligation I should / ought to see a doctor. I have a terrible headache.
advice You should / ought to revise your lessons
logical conclusion He should / ought to be very tired. He’s been working all day long.
had better advice You ‘d better revise your lessons

Modal Verbs – ISE II Trinity Grammar Function

Remember

Modal verbs are followed by an infinitive without “to”, also called the bare infinitive.

Examples:

  • You must stop when the traffic lights turn red.
  • You should see to the doctor.
  • There are a lot of tomatoes in the fridge. You need not buy any.

Modals in the present and past

Generally speaking modals in the past have the following form:

  • modal + have + past participle
  • Present:
    You should see a doctor.
  • Past:
    You should have seen a doctor

Except for modals that express obligation,ability and lack of necessity:

  • Obligation:
    Present = I must / have to work hard. — Past = I had to work hard.
  • Ability:
    Present = I can run fast. — Past = I could run fast when I was young.
  • Lack of necessity:
    Present = You don’t have to / needn’t take your umbrella. — Past = You didn’t have to / didn’t need to take your umbrella.
Modals in the Present Modals in the Past
Obligation You must / have to stop when the traffic lights are red. You had to stop.
Advice You should see a doctor. You should have seen a doctor
Prohibition You mustn’t smoke here. You mustn’t have smoked there.
Ability I can run fast. I could run fast. now I am old.
Certainty He has a Rolls Royce. He must be very rich.
He can’t be American. His English is terrible.
He must have been rich. He had a big house and an expensive car.
He can’t have written that poem. He was illiterate.
Permission Can I go out? She could drive her father’s car when she was only 15.
Possibility It may / can / could / might rain. It’s cloudy. I guess it may / can / could / might have been Lacy on the phone.
Lack of necessity You don’t have to / needn’t buy any tomatoes. There are plenty in the fridge. You didn’t have to / didn’t need to buy tomatoes.

Modal Verbs – ISE II Trinity Grammar Function